The present embodiments relate to a local coil for a magnetic resonance tomography (MRT) system.
Magnetic resonance tomography devices for examining objects or patients using magnetic resonance tomography (MRT, MRI) are described, for example, in DE10314215B4.
In MR tomography, images with a high signal-to-noise ratio may be recorded using local coils (e.g., loops). In this way, the excited nuclei induce a voltage into antennas of the local coil. The induced voltage is amplified with a low noise preamplifier (LNA) and is routed via cables to the receiving electronics at the MR frequency. High field systems are also used in high resolution images to improve the signal-to-noise ratio, the basic field strengths of which may lie at 3 Tesla or more. Since more coil elements (loops) may be connected to an MRT receiving system than there are receivers available, a switching matrix (e.g., RCCS) is installed between the receiving antennas and the receiver. This routes the currently active receiving channels to the existing receiver. As a result, more coil elements than there are receivers available may be connected, since with a whole body coverage, only the coils that are in the field of view (FOV) and/or in the homogeneity volume of the magnet are to be read out.
The individual antenna elements are also referred to as coil elements. An antenna that may include one or more coil elements (e.g., array coil) is referred to as a “coil” or “local coil.” A local coil includes, for example, coil elements, the preamplifier, further electronics and cabling, the housing and may include a cable with a plug, by which the local coil is connected to the system. “System” below may be the MRT system. “Parallel imaging methods” (e.g., Siemens product name iPAT) are used in MR to reduce the measuring time. These use the spatial resolution of the individual receiving coil elements in order to reduce the measuring time. The greater the number of coil elements on a given geometry, the more rapid acceleration techniques may therefore be used. The motivation in developing high channel local coils (e.g., including many channels) therefore results. The increasing number of channels of local coils also determines (e.g., since the patient geometries remain similar) that the individual coil elements become smaller. Smaller coil elements provide a higher SNR than larger elements in the vicinity of the coil. The increase in the number of channels in a local coil is therefore advantageous in terms of an improved image quality in the vicinity of the receiving antennas and an improved image quality overall during use of iPAT, for example.
In order to be able to evaluate the MR signals emitted by the spin in the examination object, the local coils including a plurality of individual loops (e.g., individual antennas) are used. In this way, each of the individual loops is equipped with evaluation electronics that may occupy between 20 cm2 and 30 cm2 of space. Since the trend in MR diagnostics is moving toward increasingly higher acceleration factors and thus to local coils with ever more channels, the overall dimensions of the local coil do not change or only change insignificantly. An increasingly higher electronics density on the local coils results. Since the electronic components may be embodied as rigid printed circuit boards, the local coils with a higher number of channels are also more inflexible. This is problematic in the case of multipurpose local coils or local coils for abdomen imaging. These should be embodied as flexibly as possible in order to be able to be effectively adjusted to significantly fluctuating anatomies of the examination objects in order thus to achieve the highest possible image quality.
With some flexible local coils, attempts are made to embody the rigid areas of the electronic components to be as small as possible in order to obtain as high a residual flexibility of the local coil as possible. A further known possibility of achieving high coil flexibility is not to connect the electronic components directly to the individual loops (e.g., antennas) but instead in an additional housing that may be placed outside of the examination region. This provides for a very flexible embodiment of the local coil.